A crushing blade for crushing a wood and a composite material of a wood based material, a rotary cutting tool, such as a circular saw blade, which is used in a cutting work, and other planing tools, such as a planer knife, selectively use a bearing steel, tool steel, cemented carbide alloy or the like as its substrate. It is popular to perform a process, such as PVD, of applying a hard fundamental layer containing chromium nitride (CrN) to the rake faces or clearance faces of the wood cutting tools, such as the crushing blade and the cutting blade, for the purpose of improving the sharpness, and the lasting and improved cutting life thereof.
For example, Patent Literature 1 has proposed formation of a chromium nitride hard fundamental layer on either the clearance face or the rake face of a wood cutting tool having a high speed tool steel, a cemented carbide alloy or the like as the substrate thereof to thereby suppress aging-dependent wearing of the cutting edge.